Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$121.28	11.702%	$135.4722	$135.47	$135.45	$135.50
Purchase #2	$111.54	5.365%	$117.5241	$117.52	$117.50	$117.50
Purchase #3	$152.75	10.208%	$168.3427	$168.34	$168.35	$168.30
Purchase #4	$138.79	9.719%	$152.279	$152.28	$152.30	$152.30
Purchase #5	$173.92	7.862%	$187.5936	$187.59	$187.60	$187.60
Purchase #6	$152.61	6.142%	$161.9833	$161.98	$162.00	$162.00
Purchase #7	$97.43	3.228%	$100.575	$100.58	$100.60	$100.60
7 purchase totals =	$948.32		$1,023.7699	$1,023.76	$1,023.80	$1,023.80